They're doing it to evade customs. The concentrations in these pills are extremely high and aren't meant to be taken by users. They're meant to be brought into the US in an inconspicuous package, crushed up and then mixed in with heroin thats been cut with whatever. Dealers aren't hurting for customers, by any stretch. The opposite problem is usually the sticking point for them: demand outstrips supply. There's a lot of weird hysteria around fentanyl lately where everybody thinks that dealers are hanging around trying to hook kids with colorful pills but that's not how it works. That's never been how it worked.